This invention relates to the field of electrically operated hoisting and pulling apparatus and electrical control circuits associated with such apparatus.
Electrically operated hoisting and pulling devices and the control apparatus used with such devices have been continuously improved in the electrical art since the inception of electric motors. Generally devices of this type consist of an electric motor coupled through mechanical gearing to a flexible tension member such as a chain or rope or cable which can in turn be attached to a load object. In many applications the hoisting and pulling apparatus also includes mechanical clutch and brake members which allow precise control over the hoisting or pulling motion and also eliminate coasting and reverse movement under the influence of heavy loads. Generally hoisting and pulling apparatus of this type may be designed to employ a variety of electrical energy sources including direct current, alternating current, multiphase alternating current and combinations of these energy sources.
A particular form of hoisting and pulling apparatus which is found useful with heavy loads and long distances in an out-of-doors environment is commercially available as a Beebe (TM) winch; the name Beebe is used by Beebe International Inc. of Seattle, Wash. as a trademark. The winch embodied in the present invention includes a winding drum and steel cable and is usable in pulling loads over relatively large distances as might be needed for transferring guided missiles between a hauling trailer and a holding or launching facility for example. Other uses of the invention are of course possible.
The control circuit portion of the invention can of course be used with other types of hoisting and pulling apparatus and with other forms of motor driven equipment which require precise starting and stopping characteristics and retention of an attained position of the driven load. Uses such as machine tool component positioning, radio antenna positioning, and material feeding operations are examples of such alternate uses.